How to insert 'NULL' values into PostgreSQL database using Python?

Question

Is there a good practice for entering NULL key values to a PostgreSQL database when a variable is None in Python?

Running this query:

mycursor.execute('INSERT INTO products (user_id, city_id, product_id, quantity, price) VALUES (%i, %i, %i, %i, %f)' %(user_id, city_id, product_id, quantity, price))

results in a a TypeError exception when user_id is None.

How can a NULL be inserted into the database when a value is None, using the psycopg2 driver?

Answer 1

With the current psycopg, instead of None, use a variable set to 'NULL'.

variable = 'NULL'
insert_query = """insert into my_table values(date'{}',{},{})"""
format_query = insert_query.format('9999-12-31', variable, variable)
curr.execute(format_query)
conn.commit()

>> insert into my_table values(date'9999-12-31',NULL,NULL)

Answer 2

Here is my solution:

text = 'INSERT INTO products (user_id, city_id, product_id, quantity, price) VALUES (%i, %i, %i, %i, %f)' %(user_id, city_id, product_id, quantity, price))

text = text.replace("nan", "null")

mycursor.execute(text)

Answer 3

A simpler approach which also is practical with high number of columns:

Let row be a list of values to be inserted that may contain None. To insert it into PostgreSQL we do as follows

values = ','.join(["'" + str(i) + "'" if i else 'NULL' for i in row])
cursor.execute('insert into myTable VALUES ({});'.format(values))
conn.commit()